Now that evolution has become an issue in the presidential campaign (in the May 3 debate among Republican presidential hopefuls, when moderator Chris Matthews asked if any candidates did not “believe in” evolution, three hands—Tom Tancredo’s, Sam Brownback’s and Mike Huckabee’s—shot up), it is always amusing when biologists put another brick in the solid wall that is evolution. The latest comes from a study in which researchers discovered clues to the evolutionary origins of the nervous system.

For anyone who just arrived from Neptune, the “nuanced” stance against evolution—that is, the one that doesn’t make you look like a complete Neanderthal—is to note that of course you know that microevolution occurs, with bacteria evolving resistance to antibiotics and mosquitoes to pesticides, for instance. It’s macroevolution—in which one species evolves into another—that gives you pause since, after all, who has seen such a thing?

The intelligent design camp also argues that some biological structures are just too darn sophisticated to have evolved through random mutation and natural selection. They must therefore have been designed by an intelligent agent. In particular, since complex structures have lots of components, how could the components have been just hanging around for eons waiting for the final component to emerge? Think of it this way: if you don’t already have all the other components of a mousetrap, why would you keep a spring around? A spring is only useful if you also have the base, the bar and the rest. This is the argument called “irreducible complexity,” and it has proved very persuasive to the public.

It’s always dangerous to base your argument on some version of “scientists have never found X” (with X in this case being components of a complex structure existing and serving a function before the rest of the components showed up). That’s because those darn scientists keep making discoveries. If you want to say they “have never found . . . ,” you’d better understand that what you really mean is “they haven’t found it yet.”